Most consoles generally have at best a few games that define the system. Generally these games are either console specific or are simply the best version available. For me ....
N64 = Super Mario 64, Mario Kart, Banjo series, Zelda - OOT
SNES = Donkey Kong Country series, Mario All-Stars
PS1 = Gran Turismo, NFS Hot Pursuit
PS2 = None that I can think of .....

Dreamcast = Soul Calibur, Hydro Thunder, House of the Dead 2, SF 2049
As a result you can make a case for owning a particular console if you have a desire to play/own those particular games that rock your boat so to speak. Console emulation generally isn't of a suitable standard to replace a console although PS1 emulation is cetainly getting up there. But for me it's the controllers that really count. N64/Dreamcast emulation is crap and I love the original controllers.
So owning a console just for one game isn't an issue for me ...... especially when you can pick one up in their twilight years for pennies .... $30 for a Dreamcast is dirt cheap. Just make sure that the unit has a good GD-Rom laser as they're hard to replace now .....